Plow hitch



E. V. COLLINS Sept. 29, 1953 PLOW HITCH 4 Sheets-Sheet 1 Filed June 3,1950 INVENTOR. l dga r M Collins BY xmg d E. v. COLLINS 2,653,531

PLOW HITCH 4 Sheets-Sheet 2 Ch mu Z 8 4 No a a A a I Q 1/4 a f i 4/ r wM KA M Sept. 29, 1953 Filed June 3, 1950 E. V. COLLINS Sept. 29, 1953FLOW HITCH 4 Sheets-Sheet 5 Filed June 5, 1950 INVENTOR. Edgar M CollinsBY Fig.7

E. V. COLLINS Sept. 29, 1953 PLOW HITCH 4 Sheets-Sheet 4 Filed June 5,1950 INVENTOR. dsar M Collins any Patented Sept. 29, 1953 UNITED STATESPATENT OFFICE PLOW HITCH Edgar V. Collins, Ames, Iowa Application June3, 1950, Serial No. 165,922

10 Claims.

This invention relates generally to tractor hitches and in particular toa hitch for connecting a farm tractor with a ground working farmimplement such as a plow, cultivator, lister, and the like.

In the general use of a ground working farm implement, such as a plow,for example, appreciable difficulty is encountered in contour plowing,or plowing requiring short radius turns, due to the inability of theplow to follow the tractor in the turn. This objection is generally theresult of the side thrust of the plow acting to limit the effectiveturning action of the tractor steering Wheels, so that the side thrusttakes the steering of the tractor away from the trac- :1

tor steering wheels in a short turn. In other words, after the tractorhas been turned to a certain point, any further steering action isineffective to accomplish any sharper turning radius due to the steeringwheels being merely pushed or skidded in a turn having a radius greaterthan that called for by the turned position of the steering wheels.Further evidence of this condition is found in the fact that the widthof the cut made by the plow in the turn, is of a different widthrelative to the cut made by the plow during the straight advance of thetractor.

It is an object of this invention, therefore, to provide for an improvedtractor hitch.

A further object of this invention is to provide a tractor hitch for aground working implement which maintains a substantially uniform widthof out in both a straight line and short turn operation of the tractor.

Another object of this invention is to provide a tractor hitch for aplow capable of controlling the action of the plow so as to maintain thedepth and width of the plow cut substantially uniform for an operationof the tractor in an arcuate path over an uneven or irregular groundsurface.

Another object of this invention is to provide a hitch for connecting aplow with a tractor which is capable of controlling the suction of theplow so that the depth of the furrow being cut by the plow issubstantially uniform for a travel of the tractor over an uneven groundsurface.

Another object of this invention is to provide a hitch for connecting aplow with a tractor such that a part of the usual sidethrust on the landside of the plow is transferred to the tractor wheels, whereby to permita plowing with a tractor equipped with a Ford hydraulic power unit;

Fig. 2 is a detail perspective view of the plow hitch, with certainparts broken away to more clearly show its construction;

Fig. 3 is a plan view of the assembly shown in Fig. 1; V

Fig. 4 is a, side elevational view of the plow hitch shown in one movedposition therefor;

Fig. 5 is a side elevational view of the plow hitch illustratedsimilarly to Fig. 4 and showing parts thereof in changed positions;

Fig. 6 is a perspective view of a modified form of the plow hitch ofthis invention with certain parts broken away for the purpose ofclarity;

Fig. '7 is a side elevational view of the plow hitch shown in Fig. 6; II

Figs. 8 and 9 are diagrammatic side elevational views of the plow hitchof Fig. 6 shown in assembly relation With a tractor; and

Fig. 10 is a side elevational view illustrated similarly to Fig. 7.

With reference to the drawings the hitch of this invention isillustrated in Fig. 1 in assembly relation with a tractor, designatedgenerally as [5, having a rear axle l6, and a plow structure, designatedgenerally as 20 including a pair of inter-connected plow beams 2| and 22and an upright frame 23. Y

The tractor illustrated is a Ford, equipped with a hydraulic power unit24 of a well known type, and having a pair of draft arms 26 and 26a withtheir front ends 21 swivelly connected at 44 to opposite sides of thedifferential housing 28. Lift links 29 are connected with the draft arms26 and 26a and with a pair of rock arms (not shown) which are actuated,on operation of the power unit 24, to lift the draft arms 26 and 26awherebyto raise and lower the plow structure 20 relative to the ground.A link 3| is pivoted at one end to a bell crank 32, and at its oppositeor rear end to the upright frame 23 on the plow structure 20. The bellcrank 32 is operatively associated with a valve mechanism 33 so thatwhen the draft on the plow or farm implement varies tending to tilt theimplement toward the tractor, the power unit 24 is actuated to raise theplow structure from the ground.

The hydraulic power lift 24 briefly discussed above is well knowncommercially and except for the utilization of the draft arms 26 and 26aforms no part of the present invention.

The hitch of this invention (Figs. 1 and 2) includes a rock shaft 36which is carried in a tubular bearing 31. Secured, as by welding, toopposite ends of the rock shaft 36 are a pair of rock arms 38 and 39which are relatively positioned so as to extend laterally outwardly inopposite directions from the rock shaft 36. Located between each rockarm 36 and 39 and an adjacent end of the tubular bearing 3'1 is aspacing collar 4|.

As best appears in Fig. l the rock shaft and rocker arm assembly isextended transversely of the plow structure 20, at a position adjacentthe front end thereof, and is secured to the plow beams 2| and 22 bymeans of U-clamps 42 extended about the tubular bearing 31 and carriedin suitable brackets 43 mounted in an oppositely arranged relation onthe plow beams 2| and 22.

As previously mentioned the front ends 2'! of the draft arms 26 areswivelled, as indicated at 44 in Fig. l, to opposite sides of thedifferential housing 28, such that the connections 44 are in linearalignment transversely of the tractor IS. The rear end 46 of the draftarm 26a is swivelled adjacent the free end of the rock arm 38 on aswivel pin 41 extended laterally outwardly from the rock arm 38 in aparallel relation with the rock shaft 36. The rear end 48 of the draftarm 26 is swivelled on the rock arm 39, at a position intermediate theends thereof, on a swivel pin 49 projected laterally outwardlyfrom therock arm 39 in a parallel relation with the rock shaft 36. It is seen,therefore, that the pins 41 and 49 on the rock arms 38 and 39,respectively, are at opposite ends of the rock shaft 36.

A stabilizing or actuating arm illustrated as being of a longer lengththan the draft arms 26 and 26a (Figs. 1 and 2), has its front end 52swivelly connected at 53 on the tractor rear axle l6 at a positionspaced outwardly from the draft arm 26. The rear end 54 of thestabilizing arm 5| is swivelled adjacent the free end of the rock arm 39on a swivel pin 56 projected outwardly from the rock arm 39 in aparallel relation with the pivot pin 49. The swivels 44 for the frontends of the draft arms 26 and 26a, and the swivel 53 for the stabilizingarm 5|, are in linear alignment transversely of the tractor I5, asindicated by the line 51 in Fig. 2 whereby the arms 26, 26a and 5| aremovable in an up and down direction about a common axis and transverselyof the tractor I5. Further, the draft arms 26 and 26a are symmetricallyarranged relative to a medial line 58 extended transversely of the rockshaft 36 at a center position between the rock arms 38 and 39.

The rock arm 39 (Figs. 1 and 2) is provided with an extension arm 59extended laterally from the rock shaft 36 in the same direction as therock arm 38. When the rock shaft 36 is assembled on the beams 2| and 22,the rock arm 39 is positioned outwardly from the beam 22, while the rockarm 38 is positioned outwardly from the beam 2|. The beam 22 carries anoutwardly extended lateral bracket or projection 6| which is locatedrearwardly of the rock arm 39 and in turn rearwardly of the extensionarm 59. A coil spring 60 is connected in tension to the free end of theextension arm 59 and to the bracket 6|, with an adjusting screw 62 atthe bracket 6| providing for a variation in the tension of the spring60. The pressure of the spring 60 acting on the rock shaft 36 effects acontinuous yieldable bias on the rock shaft tending to rotate the rockshaft in one direction of rotation thereof. This pressure applied by thespring 60 on the rock shaft 36 acts to offset or counter balance theside thrust produced on the land side 15 of the plow 63 carried on thebeams 2| and 22, and which side thrust tends to move the plows 63 intothe furrow wall, or toward the left as viewed in Fig. 1.

In the operation of the hitch of this invention assume the tractor to bemoving forwardly in a straight path. For this advance of the tractor l5the plow structure 20 is in a direct following relation with thetractor, as illustrated in full lines in Fig. 3, and the draft arms 26and 26a are in a symmetrical arrangement relative to the longitudinalaxis of the tractor or the medial line 58 shown in Fig. 2. This fullline position of the plow structure 20 in Fig. 3 corresponds to itsshowing in Fig. 1, wherein it is seen that the rock arm 39 is in asubstantially vertical upright position and the extension arm 59 isprojected downwardly. From a consideration of Fig. 2 it is apparent thatthe rock arm 38 in turn is projected vertically downward.

When the tractor I5 is turned to the left the draft arms 26 and 26a andstabilizing arm 5| are moved from their full line positions shown inFig. 3 to their dotted line positions indicated at B in Fig. 3, namely,to positions inclined rearwardly from their front ends toward the leftside of the tractor.

With this movement of the arms 26, 26a and 5| in the direction of theleft hand turn, the plow structure 20 is moved so as to be pointedtoward the right side of the tractor l5, as illustrated at B by the beam22 in Fig. 3, whereby the plows 63 are steered in a following relationrelative to the turning are or radius of the tractor. Concurrently withthe movement of the arms 26, 26a and 5| to their left hand turnpositions indicated in dotted lines at B in Fig. 3, the rock shaft 36 isrocked in a clockwise direction, as viewed in Fig. 1, to its positionshown in Fig. 4 whereby to increase the pressure exerted by the spring66. However, since this rocking movement of the shaft 36 provides forthe movement of the extension arm 59 upwardly and forwardly from itssubstantially upright position shown in Fig. 1, the effective moment armof the spring 60 relative to the axis of the rock shaft 36 is reducedrelative to its effective moment arm when the extension arm is in itsdownward position shown in Fig. 1. As a result, the force applied on therock shaft 36 by the spring 60 to counter balance a part of the sidethrust produced by the plows 63 remains substantially constant.

It is seen, therefore, that the movement of the plow structure 20 in adirection transversely of the tractor 5 and away from the furrow wallfor a left hand turn maintains the plow structure in a followingrelation with the tractor in the turn whereby the width of cut made bythe plows 63 in a lefthand turn is substantially equal to the width ofthe cut made by the plows for a straight path advance of the tractor I5.

Referring to Figs. 1 and 2, in which the rock arms 38 and 39 are shownin positions for a straight line advance of the tractor, it is seen thatthe rear end 46 of the draft arm 26a is located below the rock shaft 36,while the rear end 48 of the draft arm 26 is positioned above the rockshaft 36. In a lefthand turn of the tractor the movement of the rock arm39 to its position shown in Fig. 4 takes place by virtue of the factthat the connections 49 and 56 for the draft arm 26 and stabilizing arm5|, respectively, are moved in a rearward direction, while theconnection 41 for the draft arm 26a is moved forwardly or in a reverseddirection. Since the swivel connections on the tractor rear axle l6 forthe draft arms 26 and 26a, andstabilizing arm 5| are stationary, and inlinear alignment transversely of the tractor, the stabilizing arm 5|functions as an actuating arm to move the complete plow structure towardthe left, as viewed in Fig. 1,

or toward the furrow wall to compensate for the movement of theconnections 41, 49 and 56 in response to the rocking movement of therock arms 38 and 39. This steering action on the plow structure 28 bythe complementary action of the arms 26, 26a and 5|, and rocker shaftassembly, provides for an eifective steering of the tractor l5 by virtueof the reduction of the tendency of the plow side thrust to steer thetractor in short radius turns.

For a righthand turn of the tractor IS the rear ends of the draft arms26 and 28a, and stabilizing arm 5| are shifted transversely of thetractor IS in the direction of the righthand turn, from their full linesshown in Fig. 3 to their dotted line posi tions shown in the same figureand indicated at C, to in turn move or steer the plow structure 28 sothat it points toward the left hand side of the tractor as indicated atC by the plow beam 22 in Fig. 3. For this movement of the draft arms 26and 26a and stabilizing arm 5|, the rocker arm 39 is moved in acounterclockwise direction from its position shown in Fig. 1, to itsposition shown in Fig. 5. The steering movement of the plow structure 29in a direction toward the furrow wall, during a right hand turn of thetractor, is thus effected by the actuating action of the stabilizing arm5|, to swing the plow structure in response to the reversed movements ofthe rock arms 38 and 39 and the draft arms 26a and 26, respectively.Referring to Fig. 5 it is seen that the tension in the spring is reducedconcurrently with an increase in the effective turning movement of theextension arm 59 relative to the axis of the rock shaft 36 whereby tomaintain substantially uniform the pressure of the spring 69 applied onthe rock shaft 36.

With the steering movement of the plow structure 20 towards the left, asviewed in Fig. 1, or toward the furrow wall, for a righthand turn, thewidth of the cut taken by the plows 63 is maintained substantially thesame relative to the width when the tractor I5 is operating in astraight line path. Thus, without the plow hitch of this invention, fora righthand turn the plow structure would tend ot move away from thefurrow wall so as to take a narrow cut relative to the cut taken for astraight line advance of the tractor. Further, the tractor is capable ofbeing operated through a shorter turning radius since the plow structure28 is maintained in a following relation with the tractor during therighthand turn.

The modified form of the invention shown in Figs. 6-10, inclusive, issimilar in many respects to the plow hitch shown in Fig. l butadditionally provides for a control of the suction action of the plowwhereby a furrow of substantially uniform depth is maintained for atravel of the tractor over an uneven ground surface.

Similar numerals of reference will be used, therefore, to designate likeparts- With reference to Fig. 6 the modified form is shown as includingwhat will be termed a hanger structure 10 having a triangular horizontalframe H with its apex 12 at the rear end thereof and its base member 13at the front end thereof. An upright frame 14 extended upwardly from thebase 13 has its top end 16 pivotally connected, as shown in Fig. 8, witha top link 11 which is associated with a Ford power lift 24 in allrespects similar to the top link 3| shown in Fig. 1.

The base member 13 is provided at its opposite ends with a pair ofdownwardly projected bearing straps or arms 18 and 18a which are formedwith transversely aligned arcuate slots 19 for a purpose which willappear later. As shown in Figs. '7 and 10 the apex 12 of the frame 1|terminates in a downwardly and rearwardly projected bearing armextension 8| that is formed with an arcuate slot 82 which is reverselyinclined relative to the aligned slots 19 formed in the bearing arms 18and 18a. The free or lower ends of the front bearing arms 18 and 19a areformed with transversely aligned holes 84 for rotatably receiving atubular bearing 86 (Fig. 6).

' A rock shaft 81 extended through the bearing sleeve 86 has secured toits opposite ends rock arms 38 and 39 which are arranged in all respectssimilar to the rock arms 38 and 39 for the rock shaft 36 described inFig. 1. Further, and similarly to the plow hitch shown in Fig. 1, thedraft arm 26a is pivotally connected to the free end of the rock arm 38,and the draft arm 28 and stabilizing arm 5| are pivoted on the pins 49and 59, respectively, provided on the rockarm 39. The

tension spring 60 (Fig. 6) has its front end connected to the rock armextension 59 and its rear end connected to a bracket 88 projectedlaterally from the apex 12 of the horizontal frameH of the hangerstructure 18. The plow beams 2| and 22 are inter-connected adjacenttheir rear ends by a brace member 89 and adjacent their front ends by atie rod 9| (Figs. 6 and '7). Mounted about the tie rod 9| is a rollertube 92.

As best appears in Fig. 6 the plow beams 2| and 22 are arranged atopposite sides of the hanger structure 1|) with the tie rod 9| androller tube 92 extended through the arcuate slots I9 formed in thebearing arms 18 and 18a. Positioned within the arcuate slot 82, formedin the rear extension 8| of the frame H, is a roller which is carried ona stub shaft 93 mounted on the plow beam 22 at a position adjacent therear end thereof. Each of the rollers 92 and 95 has associated thrustwashers 96 which are engageable with the left sides of the arm 18a andrear extension arm 8|, respectively, as viewed in Fig. 6, or with thefront sides of these arms as viewed in Fig. 7. Likewise, a thrust collar98 is fixed to the tubular bearing 86 for engagement with the right sideof the arm 18a as viewed in Fig. 6. This arrangement of the thrustwashers 96 and thrust collar 98 counteracts the action of the spring 60to pull the plows 63 toward the left, as viewed in' Fig. 6.

The operation of the plow hitch of Fig. 6 for accomplishing a shortradius turn of the tractor during a plowing operation, with amaintaining of a substantially uniform furrow width, is similar in allrespects to such operation previously described in connection withFig. 1. A further description of this operation thus is believed to beunnecessary.

In the operation of the modified form of the hitch shown in Fig. 6 forcontrolling the suction action of the plows 63 for a travel of thetractor over an uneven groundsurface it will be noticed fromFigs. 7 and10 that the arcuate slots 19 and 92 are reversely inclined, namely, thefront slots 19 are inclined upwardly and rearwardly, while the rear slot82 is inclined downwardly, and rearwardly. The inclination of the slots19 and 82 are empirically developed on the theory that the hypotheticalpoint of application of the pulling force on the plows 63 for a straightline pull without any suction action, takes place at the point indicatedat 99, in Fig. 10, located centrally between the plows 63 andconstituting a common center for the slots I9 and 82.

The slot 82 in one embodiment of the invention, is formed on a radius oftwenty-four and five-sixteenths inches, while the slots 19 are formed ona radius of twenty-three inches. In this embodiment the point 99 islocated seventeen and one-half inches downwardly from the lower side ofthe horizontal frame H.

In the operation of the depth or suction control for the plows 63, whenthe tractor I5 is travelling over level ground the rollers 92 and 95 arelocated substantially intermediate the ends of their respective slots 19and 82 as shown in Fig. 10. Should the tractor front wheels IOI (Fig. 9)drop within a depression, indicated at 102, the frame 10 is movedclockwise relative to a transverse axis through the point 99 so that theroller 95 is located at the lower end of the slot 82 and the roller 92at the upper ends of the slots 79 whereby the suction of the plows. 63remains unchanged to thus maintain the depth of the furrow, indicated atI03, uniform. In other words, the frame 10 is moved relative to theplows.

When the tractor rear wheels 65 drop into the depression I02, asillustrated in Fig. 8, the frame 10 is rotated in a counterclockwisedirection about a transverse axis through the point 99 so that theroller 95 takes a position at the upper end of the slot 82 and theroller 92 a position at the lower ends of the slots 19, with this actionagain resulting in no change in the suction action of the plows 63.

This movement of the frame 10 relative to the plows eliminates anystepping or chattering action of the plows 63 by acting to maintain theplows in adjusted suction positions and against any tipping movement inresponse to a travel of the tractor over uneven ground surfaces.

Although the invention has been described with specific reference to aplow, it is to be understood that it can be used with any farm implementof trailing type having a ground working tool thereon, such as aplanter, cultivator,

lister or disc.

It is to be further understood that although the invention has beendescribed with respect to several embodiments thereof, it is not to beso limited since changes can be made therein which are within the fullintended scope of this invention as defined by the appended claims.

I claim:

1. A :plow attachment for a tractor having a rear axle, comprising aplow frame structure located rearwardly of said axle and movablysupported from said tractor for up and down and transverse swingingmovement, a transverse rock shaft carried adjacent the front end of saidframe, a pair of rock arms mounted on said rock shaft in an axiallyspaced relation, with said rock arms being extended in oppositedirections laterally of said shaft, a third rock arm on said shaft, apair of oppositely arranged,

transversely spaced connecting .arms movably connected to said pair ofrock arms and to said axle, a stabilizing arm movably connected to oneof said rock arms and to said axle at a position spaced outwardly fromthe connection with said axle of the connecting arm corresponding tosaid one rock arm, and yieldable means connected at one end to saidthird rock arm and at its opposite end to said frame at a positionrearwardly of said rock shaft.

2. A plow attachment for a tractor having a. rear axle, including aplow-carrying frame located rearwardly of said axle and supported fromsaid tractor for up and down and transverse swinging movement, atransverse rock shaft on said frame having a pair of axially spaced rockarms projected laterally in opposite directions therefrom, connectingarms corresponding to said rock arms, means movably connecting saidconnecting arms to said axle and to said rock arms, a stabilizing armmovably connected to said axle and to one of said rock arms, and meansfor yieldably urging said shaft in one direction of rotation therefor.

3. A plow attachment for a tractor having a rear axle including aplow-carrying frame supported from said tractor for up and down andtransverse swinging movement rearwardly of said axle, a transverse rockshaft carried adjacent the front end of said frame, a pair of axiallyspaced rock arms on said shaft projected laterally in oppositedirections from said shaft, a pair of draft arms corresponding to saidrock arms movably connected to said axle and to said rock arms atpositions spaced substantially equal distances laterally from the axisof said rock shaft, a stabilizing arm movably connected to one of saidrock arms at a position spaced laterally outwardly from the connectiontherewith of a corresponding draft arm, and to said axle at a positionspaced outwardly from the connection with the axle of said correspondingdraft arm, and means for yieldably urging said shaft in one direction ofrotation therefor.

4. A plow attachment for a tractor having a rear axle including aplow-carrying frame supported from said tractor at a position rearwardlyof said axle, a transverse rock shaft carried adjacent the front end ofsaid frame having a pair of longitudinally spaced rock arms arranged atsubstantially equal distances to opposite sides of the longitudinalcenter line of said frame, a pair of longitudinally extended draft armsof substantially equal lengths, corresponding to said rock arms, andhaving their rear ends movably connected to said rock arms and the frontends thereof movably connected to said axle, with the connections ofsaid draft arms to said axle being at substantially equal distances fromopposite sides of said longitudinal center line, and a stabilizing armmovably connected to said axle and to one of said rock arms.

5. A plow attachment for a tractor having a rear axle including a framefor carrying a ground working tool, a transversely extended rockableunit on said frame having laterally extended arms, a hitch means movablyconnected to said tractor and to said arms, a stabilizing member movablyconnected to said tractor and to one of said arms for rocking saidrockable unit, and means for yieldably urging said rockable unit in onedirection of rotation therefor such that the pressure of said yieldablemeans on said rockable unit is substantially constant for any movedposition of said rockable unit.

6. In a pull attachment for a tractor including a frame for carrying aground working tool rearwardly of the tractor, a transversely extendedrockable unit mounted on said frame having a pair of oppositely extendedlateral arms, a pair of draft arms movably connected to the tractor andto said pair of lateral arms, an actuating arm member movably connectedto said tractor and to one of said lateral arms such that the connectionat the rear end of said actuating arm is vertically disposed from theaxis of said rockable unit when the attachment is in a straight pullposition therefor, yieldable means for urging said rockable unit in onedirection of rotation thereof, and means for maintaining the pressure ofsaid yieldable means on said rockable unit substantially constant forany moved position of said rockable unit.

7. A pull attachment for a tractor including a frame for carrying aground Working tool rearwardly of the tractor, a transversely extendedrockable means on said frame having a pair of rock arms thereon, a hitchmeans including a pair of draft arms of the same length having the frontends thereof movably connected to said tractor and the rear ends thereofmovably connected to said pair of rock arms, and a stabilizing arm of adifferent length than said draft arms movably connected at the front endthereof to the tractor and having the rear end thereof movably connectedto one of said rock arms, with i the connections at the front ends ofsaid draft arms and at the front end of said stabilizing arm being inlinear alignment transversely of the tractor, and said one rock armbeing in an upright position when the attachment is in a straight pullposition therefor.

8. In combination with a tractor, a frame for carrying a ground workingtool rearwardly of the tractor, a transversely extended rockable meanson said frame having a pair of rock arms thereon, means for swingingsaid frame transversely of the tractor during a turning movement thereofsuch that the frame is swung toward the tractor side which is on theinside of the turn including a pair of oppositely arranged draft arms ofa like length movably connected to the tractor and to said pair of rockarms and an actuating arm movably connected to the tractor and to one ofsaid rock arms such that when the attachment is in a straight pullposition therefor, said one rock arm is in a substantially uprightposition, with the connections of said pair of draft arms and of saidactuating arm with the tractor being in alignment transversely of thetractor, said means for swinging said frame also including means actingon said rockable means to maintain a substantially uniform andunidirectional turning pressure thereon at any moved position therefor.

9. In combination with a tractor including a frame for carrying a groundworking tool, a hitch means for connecting said frame to the tractorincluding a pair of transversely spaced draft arms, a transverselyextended rock shaft on said frame having a pair of axially spaced rockarms extended in opposite directions laterally therefrom, means movablyconnecting the rear ends of said draft arms to said rock arms, othermeans movably connecting the front ends of said draft arms to thetractor, with said draft arms being disposed in equi-distant lateralrelation to and on either side of the central draft plane of thetractor, and a stabilizing arm movably connected at one end to thetractor and at its opposite end to one of said rock arms, with theconnections of said draft arms and stabilizing arm with the tractorbeing in alignment transversely of the tractor.

10. In combination with a ground Working implement to be pulled by atractor having a main frame supported on the tractor for up and down andtransverse swinging movement, a transversely extended shaft on saidframe having a pair of axially spaced rock arms mounted thereon, withsaid rock arms being extended laterally in opposite directions from saidshaft, a third rock arm on said shaft, a pair of longitudinally extendeddraft arms having the corresponding ends thereof movably connectedrespectively to said tractor and to said pair of rock arms to permit upand down movement and limited transverse movement of said frame, astabilizing arm having one end movably connected to one of said rockarms and its opposite end movably connected to the tractor, with theconnections of said stabilizing arm and draft arms with the tractorbeing in linear alignment transversely of the tractor, and spring meansconnected to said third arm and to said frame to maintain auni-directional yieldable pressure on said rock shaft.

EDGAR V. COLLINS.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,877,958 Pawl Sept. 20, 1932 2,223,002 Ferguson Nov. 26, 19402,296,209 Kriegbaum et a1. Sept. 15, 1945 2,379,225 Frags, June 26, 19452,530,565 Briscoe Nov. 21, 1950

